Epoxy containing compounds are known to be curable using various cationic initiator systems. Smith, in U.S. Pat. No. 4,256,828, describes photopolymerizable compositions that contain epoxides, an organic compound with hydroxyl functionality, and a photosensitive aromatic sulfonium or iodonium salt of a halogen containing complex ion. Hayase et al., U.S. Pat. No. 4,835,193, describes photopolymerizable epoxy resin compositions that comprise an epoxy resin and a heteropoly-acid aromatic sulfonium salt as the photocuring catalyst. In WO 95/14716 Neckers et al. describe photohardenable compositions that comprise a cationically polymerizable compound, a xanthene or fluorone dye, a hydrogen donor, and an onium salt. Palazzotto et al., U.S. Pat. No. 5,545,676, describes addition polymerization of free-radically polymerizable materials. The photoinitiator system described in that patent comprises an aryliodonium salt, a sensitizer, and an electron donor having an oxidation potential less than or equal to that of p-dimethoxybenzene.
PCT published application No. WO 96/13538 describes a system for curing epoxy compounds by exposure to visible light by use of a system comprising an aryliodonium salt and a sensitizer. Comparative Example 34 of this disclosure describes the use of one of the initiator systems of Palazzotto et al., U.S. Pat. No. 5,545,676 in an epoxy/polyol resin system. N,N-dimethylbenzylamine is used as the electron donor. The results of this experiment indicated that the use of this amine donor tended to retard the cure of the resin system.
Suppliers of cationically cured resins expressly warn against using organic amines in photoinitiated epoxy resins. An example of such a warning is found in Union Carbide literature regarding Cyracure.RTM. cycloaliphatic epoxides.